Radiometric Ages and Stratigraphic Sequence of Volcanic and Plutonic Rocks, Southern Nye and Western Lincoln Counties, Nevada

Marvin, Richard F.; Byers, F.M.; Mehnert, Harald H.; Orkild, P.P.; Stern, T. W.

doi:10.1130/0016-7606(1970)81[2657:raasso]2.0.co;2

Cited by 47 publications

(20 citation statements)

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“…It may correspond with the Fraction Tuff (Orkild and Maldonado, unpublished report), or it may be a previously unrecognized unit of the Crater Flat Tuff (B. Crowe, personal communication, 1978). It is somewhat similar, petrographically, to the Redrock Valley Tuff (Byers et al 1976; Marvin et al, 1970), but a positive correlation cannot be made on the basis of the limited petrographic data. B. Crater Flat Tuff 1.…”

mentioning

confidence: 93%

Petrology of tuff units from the J-13 drill site, Jackass Flats, Nevada

Heiken¹,

Bevier²

1979

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confidence: 93%

Petrology of tuff units from the J-13 drill site, Jackass Flats, Nevada

Heiken¹,

Bevier²

1979

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“…The regional geothermal gradient probably reached a maximum during culminating ash-flow eruptions of the Paintbrush and Timber Mountain Tufts between 11.1 and 13.3 m.y. ago (Byers et al, 1976;Marvin et al, 1970). The upward displacement and thinning of diagenetic zones northward is likely due to a higher geothermal gradient in northern Yucca Mountain which was closer to the locus of silicic volcanism.…”

Section: Factors Controlling Diagenesismentioning

confidence: 99%

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Broxton

Bish

Warren

1987

Clays and clay miner.

121

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Abstract--Yucca Mountain is being studied as a potential site in southern Nevada for an underground, high-level nuclear waste repository. A major consideration for selecting this site is the presence of abundant zeolites in Miocene ash-flow tufts underlying the region. Beneath Yucca Mountain four diagenetic mineral zones have been recognized that become progressively less hydrous with depth.Zone I, the shallowest zone, is 375-584 m thick in the central part of Yucca Mountain, but 170 m thick to the north. Zone I contains vitric tufts that consist of uualtered volcanic glass and minor smectite, opal, heulandite, and Ca-rich clinoptilolite. Zone II thins south to north from 700 to 480 m and is characterized by complete replacement of volcanic glass by clinoptilolite with and without mordenite, and by lesser amounts of opal, K-feldspar, quartz, and smectite. Zone III thins south to north from 400 to 98 m thick and consists of analcime, K-feldspar, quartz, and minor calcite and smectite. Heulandite occurs locally at the top of zone III in the eastern part of Yucca Mountain. Zone IV occurs in the deepest structural levels of the volcanic pile and is characterized by albite, K-feldspar, quartz, and minor calcite and smectite.Clinoptilolite and heulandites in zone I have uniform Ca-rich compositions (60-90 mole % Ca) and Si:AI ratios that are mainly between 4.0 and 4.6. In contrast, clinoptilolites deeper in the volcanic sequence have highly variable compositions that vary vertically and laterally. Deeper clinoptilolites in the eastern part of Yucca Mountain are calcic-potassic and tend to become more calcium-rich with depth. Clinoptilolites at equivalent stratigraphic levels on the western side of Yucca Mountain have sodic-potassic compositions and tend to become more sodium-rich with depth. Despite their differences in exchangeable cation compositions these two deeper compositional suites have similar Si:A1 ratios, generally between 4.4 and 5.0. Analcimes have nearly pure end-member compositions, typical of these minerals formed by diagenetic alteration of siliceous volcanic glass; however, K-feldspars are Si-rich compared to the ideal feldspar formula.Bulk-rock contents of Si, Na, K, Ca, and Mg of zeolitic tufts generally differ significantly from stratigraphically equivalent vitric tufts, suggesting that zeolite diagenesis took place in an open chemical system. Both the whole rock and the clinoptilolite are relatively rich in Ca and Mg in the eastern part of Yucca Mountain and rich in Na in the western part. The Ca-and Mg-rich compositions of the zeolitized tufts in the eastern part of Yucca Mountain may be due to cation exchange by the sorptive minerals with ground water partially derived from underlying Paleozoic carbonate aquifers.Diagenetic zones become thinner and occur at stratigraphically higher levels from south to north across Yucca Mountain, probably due to a higher geothermal gradient in the northern part of the area. The diagenetic zones were established when the geothermal gradient was greater than it ...

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“…Total thickness of the Harmony Hills Tuff is ~81 m in Hackberry Canyon, where it rests on a basalt flow breccia (unit Tbb). Radiometric analyses of the Harmony Hills Tuff from the surrounding region yielded an average age of 21 Ma (Armstrong, 1970;Noble and McKee, 1972;Marvin et al, 1970).…”

Section: Appendix Description Of Map Unitsmentioning

confidence: 99%

“…In the upper half of the section there are local lenses of coarse impure sandstone or wacke as thick as 3 m. Maximum thickness is 43 m near Vigo. Hiko Tuff has yielded K-Ar ages of 18-20 Ma (Armstrong, 1970;Noble and McKee, 1972;Marvin et al, 1970).…”

Section: Appendix Description Of Map Unitsmentioning

confidence: 99%

Geologic map of the east-central Meadow Valley Mountains, and implications for reconstruction of the Mormon Peak detachment, Nevada

Swanson

Wernicke

2017

Geosphere

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The role of low-angle faults in accommodating extension within the upper crust remains controversial because the existence of these faults markedly defies extant continuum theories of how crustal faults form, and once initiated, how they continue to slip. Accordingly, for many proposed examples, basic kinematic problems like slip direction, dip angle while active, and magnitude of offset are keenly debated. A well-known example is the Miocene Mormon Peak detachment and overlying Mormon Peak allochthon of southern Nevada (USA), whose origin and evolution have been debated for several decades. Here, we use geologic mapping in the Meadow Valley Mountains to help define the geometry and kinematics of emplacement of the Mormon Peak allochthon, the hanging wall of the Mormon Peak detachment. Pre-extension structural markers, inherited from the east-vergent Sevier thrust belt of Meso zoic age, are well suited to constrain the geometry and kine matics of the detachment. In this study, we add to these markers a newly mapped Sevier-age monoclinal flexure preserved in the hanging wall of the detachment. The bounding axial surfaces of the flexure can be readily matched to the base and top of the frontal Sevier thrust ramp, which is exposed in the footwall of the detachment to the east in the Mormon Mountains and Tule Springs Hills. Multiple proxies for the slip direction of the detachment, including the mean tilt direction of hanging wall fault blocks, the trend of striations measured on the fault plane, and other structural features, indicate that it is approximately S77°W (257°). Given the observed structural separation lines between the hanging wall and footwall, this slip direction indicates 12-13 km of horizontal displacement on the detachment (14-15 km net slip), lower than a previous estimate of 20-22 km, which was based on erroneous assumptions in regard to the geometry of the thrust system. Based on a new detailed map compilation of the region and recently published low-temperature thermochronologic data, palinspastic constraints also preclude earlier suggestions that the Mormon Peak allochthon is a composite of diachronously emplaced, surficial landslide deposits. Although earlier suggestions that the initiation angle of the detachment in the central Mormon Mountains is ~20°-25° remain valid, the geometry of the Sevier-age monocline in the Meadow Valley Mountains and other structural data suggest that the initial dip of the detachment steepens toward the north beneath the southernmost Clover Mountains, where the hanging wall includes kilometer-scale accumulations of volcanic and volcaniclastic strata.

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Radiometric Ages and Stratigraphic Sequence of Volcanic and Plutonic Rocks, Southern Nye and Western Lincoln Counties, Nevada

Cited by 47 publications

References 0 publications

Petrology of tuff units from the J-13 drill site, Jackass Flats, Nevada

Petrology of tuff units from the J-13 drill site, Jackass Flats, Nevada

Distribution and Chemistry of Diagenetic Minerals at Yucca Mountain, Nye County, Nevada

Geologic map of the east-central Meadow Valley Mountains, and implications for reconstruction of the Mormon Peak detachment, Nevada

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